@kookyleo/plantuml-little-web

Browser/Node wasm-bindgen wrapper around the plantuml-little Rust crate — converts PlantUML source to SVG strings without a JVM, with byte-exact parity to the upstream Java PlantUML for the supported diagram set.

The wasm itself delegates Graphviz layout to @kookyleo/graphviz-anywhere-web via a small JS bridge, so you install both:

npm install @kookyleo/plantuml-little-web @kookyleo/graphviz-anywhere-web

Usage

import { Graphviz } from '@kookyleo/graphviz-anywhere-web';
import { setup, convert, version } from '@kookyleo/plantuml-little-web';

// Load the Graphviz wasm and wire it into the plantuml-little-web bridge.
const graphviz = await Graphviz.load();
setup({ graphviz });

console.log('plantuml-little-web', version());

const svg = convert(`@startuml
class A { x: int }
class B { y: string }
A --> B
@enduml`);

document.body.insertAdjacentHTML('beforeend', svg);

convert(puml) is synchronous once the Graphviz wasm is ready; it returns the raw SVG string. Any error from the Rust converter surfaces as a thrown JS Error whose message is the Rust Display text.

API

• convert(puml: string): string — render a .puml source to an SVG string.
• version(): string — the crate version embedded into the wasm.
• setup({ graphviz }) — install a Graphviz engine (anything exposing .layout(dot, format, engine)) as the backing renderer. Returns a disposer.
• installGraphvizBridge((dot, engine, format) => svg) — install a raw Graphviz bridge function directly. Useful if you're not using @kookyleo/graphviz-anywhere-web.
• hasGraphvizBridge(): boolean — check whether a bridge is installed.

How it works

Internally, plantuml-little-web contains the plantuml-little Rust converter compiled to wasm32-unknown-unknown. The Rust code depends on graphviz-anywhere, whose wasm32 target delegates all layout calls to a global JS function globalThis.__graphviz_anywhere_render(dot, engine, format). The setup() / installGraphvizBridge() helpers are what install that global.

This keeps the wasm small (no C++ Graphviz linked in) and lets you share the Graphviz wasm runtime between multiple PlantUML-like libraries.

Node.js usage

Native ESM wasm imports currently require the --experimental-wasm-modules flag:

node --experimental-wasm-modules app.mjs

Bundlers (webpack 5, Vite, Rollup, esbuild, etc.) handle the wasm import natively — the package ships with "type": "module" and points exports["."] at the ESM entrypoint.

License

Same as plantuml-little: GPL-3.0-or-later OR LGPL-3.0-or-later OR Apache-2.0 OR EPL-2.0 OR MIT.